SECT. 3] 



EASTERN BOUNDARY CURRENTS 



265 



e. Phosphate 



In most parts of the ocean, dissolved inorganic phosphorus (usually referred 

 to as "phosphate") increases with depth from very low values near the surface 

 to maximum values at depths somewhat greater than those of the oxygen 

 minima. Values at this maximum are higher in the North Pacific than elsewhere 

 in the world ocean (Redfield. 1958). In the eastern boundary currents isopleths 



(o) (b) 



c) (d) 



1000 



DISTANCE OFFSHORE (km) 



Fig. 10. Profiles across Canary Current at 24°N, October, 1957. (a)-(d) as in Fij 

 (After Fuglister, 1960.) 



of phosphate ascend toward the coast, where the highest surface values are 

 usually found. These coastal surface values in the Peru and Benguela regions 

 are commonly as high as 1-2 [xg-atoms/1. (Posner, 1957 ; Wooster and Cromwell. 

 1958; Hart and Currie, 1960) in contrast to the usual mid- and low-latitude 

 oceanic surface concentrations of 0.2 [xg-atom/1. or less. To these unusually high 

 surface nutrient concentrations is attributed the extraordinary productive 

 capacity of these regions (see page 276). 



